Mr Mitchell – who quit as Chief Whip in October over the altercation – allegedly has no confidence in the Met chief to investigate his own officers.

But last night Mr Hogan-Howe said that “for the avoidance of doubt” he would get to the bottom of the matter, no matter what.

Mr Mitchell admits swearing at an officer for refusing to open the Downing Street gates, but denies calling him a “f****** pleb”.

In a blistering attack on the police Mr Mitchell yesterday accused officers of trying to “destroy” his career as part of their ongoing campaign against the Coalition’s cuts to police budgets.

He said some police were “corrupt” and had launched a smear campaign against him.

Mr Mitchell added that the police could not be relied upon to clear his name.

It came after the officer involved in the original Downing Street row – and who wrote the log – was named yesterday as 42-year-old Toby Rowland.

Altercation: Toby Rowland (Photo: ianmcilgorm@me)

And the policeman who sent an email to his MP, falsely claiming to be a member of the public who witnessed the row as he passed with his nephew, was also named as Keith Wallis, 52.

But last night Scotland Yard Commissioner Mr Hogan-Howe, who on Saturday took a break from his holiday to be briefed on the probe, hit back.

He said the allegations about police collusion to frame the former Cabinet minister were “extremely serious” and said there were 30 officers examining whether there was a conspiracy. He added: “For the avoidance of doubt, I am determined there will be a ruthless search for the truth – no matter where the truth takes us.”

Despite claiming to have been the victim of a “stitch up” Mr Mitchell yesterday admitted the officer he swore at had threatened to arrest him.

He also accepted that he threatened the officer with further action, saying: “As I left I think I said that I would pursue the matter further the next day.”

Return: Andrew Mitchell wants his name cleared (Photo: LNP)

The two revelations back up the original police log. But Mr Mitchell claims CCTV footage undermines the police account, in which he is accused of saying: “Best you learn your f****** place. You don’t run this f****** Government. You’re f****** plebs.”

Former Police Minister Nick Herbert said the footage appears to show “there was some kind of campaign which was attempting to bring down a Cabinet minister”.

He said: “What they were trying to do was to run a wider campaign against the Government because they didn’t like the Government’s policy.” He added the “entire culture of the police” needed challenging.

Some of Mr Mitchell’s allies say he should now be returned to ministerial office. A YouGov poll shows 29% of voters agree.